Traffic volume estimates may be used for multiple purposes. Governments use traffic volume estimates as a proxy for crash rates, evaluation of infrastructure management needs, air quality, compliance and validation of travel demand model predictions. Navigation systems use traffic volume for calculating routes and generating travel times. City planners, event organizers, and developers use traffic volume to both predict and plan. Traffic volume, however, is difficult to measure and estimate. Current systems use actual observations or roadside sensors to collect traffic volume information. These methods are both expensive, limited in scope, and may need to be constantly updated as traffic patterns change.
Traffic volume data may be collected at permanent and temporary roadside sensors. At permanent sites, loop detectors, weight-in-motion sensors, and/or other equipment is installed for year-round, long-term vehicle detection. Permanent sites may be limited in that the sensors are expensive, sometimes require construction, and may only cover a fraction of the total roadway. Temporary sites may use portable sensors for periods of a day or less once every one to five years. Temporary sites may provide a snapshot of data, but not substantial information to predict or model volume over a longer period of time. The collected information collected may be accurate, but limited to a single location and only for the time period the sensor is active.
The result of the attempts to capture traffic volume data may be spotty, inconsistent, and unreliable data. Scaling a roadside sensor network to the size required to capture accurate and reliable data would require numerous sensors operating each and every hour of each and every day.